Although most individuals are resilient or recover rapidly in the aftermath of disasters or mass violence incidents, such events are associated with elevated risk of a wide range of mental and physical health-related reactions, including posttraumatic stress, panic, depression, generalized anxiety, and substance use problems. It is therefore important that disaster victims have access to safe, effective services to address-or reduce risk for the development of-disaster-related mental and physical health-risk problems. The potential value of effective, widely deliverable, and cost-efficient early interventions is considerable. However, few evidence-based early interventions have been developed, and only a small number has undergone rigorous scientific evaluation. Little is known about strategies that might be helpful within the general population broadly exposed to a disaster or mass violence incident. Recently, our research team was funded by NIDA to develop and explore the feasibility of a Web-delivered, education-based intervention designed to reduce risk for prevalent emotional and health-risk consequences in the aftermath of disasters. The intervention was piloted two years after the September 11th terrorist attacks with 325 participants who lived in the New York City area at the time of the attacks. Results were promising and supported the need for further development and evaluation. The primary purposes of the proposed project are to (a) refine and update existing modules that address symptoms of depression, PTSD, panic, and extreme worry, based on recent research and feasibility study data;(b) enhance the technical aspects of the intervention;(c) develop thorough evaluation mechanisms;and (d) conduct a population-based pilot study with baseline and six-month follow-up assessment to examine the preliminary efficacy of the intervention. Also, in preparation for future evaluation of the intervention in the early aftermath of a disaster (should the population-based pilot study yield promising data), this project would allow us to refine the innovative study design that integrates randomized controlled trial methodology with longitudinal epidemiological approaches to recruitment and assessment. Our proposed strategy to target a wide range of symptom presentations, as well as both subthreshold and diagnostic levels, is consistent with public health recommendations based on findings indicating benefits in terms of reduced health costs and greater positive outcomes associated with early intervention.